5.5-million-year-old bones found in Ethiopia
may be of earliest man
WASHINGTON Paleontologists searching the bleak desert of central Ethiopia have unearthed the fossilized bones of a 5.5-million-year-old creature that appears to be the oldest human ancestor yet discovered.
The finding has brought scientists tantalizingly close to determining what the earliest human ancestors looked like when somewhere between 5 million and 10 million years ago apes and humans diverged from a common ancestor to take separate evolutionary paths.
The Ethiopian creature, dubbed Ardipithecus ramidus kadabba (root-man ancestor), had a toe bone that indicates it walked upright a classic characteristic separating humans from apes and teeth that appeared to be evolving from apes to later human ancestors, researchers said.
Scientists have found only 11 bones from at least five different individuals including a jawbone with teeth, hand and foot bones, pieces of arm bones, and a piece of a collarbone making it impossible to determine the creature's size or appearance.
But tests show the remains are 5.2 million to 5.8 million years old, making it about a million years older than the 4.4-million-year-old Ardipithecus ramidus ramidus, found nearby in 1995 and previously the oldest human ancestor ever discovered.
Paleontologists for generations have tried to find the fossilized remains of the earliest human ancestors, to get a better understanding of the history of human evolution over the ages. They've had to piece together the picture from a scant collection of skulls, bones and bone fragments.
A detailed examination of the new bones indicates the creature is an older subspecies of Ardipithecus ramidus ramidus in the lineage leading to humans that includes the famous "Lucy," whose 3.5-million-year-old remains were discovered about 80 km north of the new find. Distinctly human species arose in Africa about 2 million years ago, while modern humans are only about 100,000 years old.
The discovery undermines the view that early human ancestors developed in a savanna-like habitat where they had to walk upright to cover large distances and develop the grinding teeth necessary to crush and digest woody reeds and grasses.
Instead, the creature lived along with ancient elephants, antelopes, horses, monkeys and rhinoceroses in what was then a lush mountain forest periodically destroyed by volcanic eruptions, said Yohannes Haile-Selassie, the University of California graduate student who made the discovery.
"It's not a carnivore, and though some of the teeth are like those of apes, it is not a specialized fruit eater, like all chimpanzees," said Haile-Selassie, who reported his findings in Thursday's issue of the journal Nature. The teeth suggest the creature dined on soft leaves and fruit.